SiO2-Al2O3-MgO-K2O-(F,Cr2O3)玻璃陶瓷的析晶

为了研究形核剂氟化物、氧化铬及其复合作用对SiO2-Al2O3-MgO-K2O系玻璃陶瓷形核和析晶的影响,采用高温熔融法制备了不同氟化物和氧化铬含量的基础玻璃,并对该基础玻璃进行了差热分析、显微分析和X射线衍射分析.结果表明:在所研究的玻璃体系中,氟化物或氧化铬的加入,都不同程度地削弱了玻璃体的结构,降低了玻璃的转变温度;当基础玻璃只含有氟化物时,玻璃在表面析出云母晶体,内部发生分相现象,而玻璃中仅含有氧化铬时,玻璃中发生整体析晶;没有氟化物的存在,不能析出云母晶体;当同时加入两种元素的物质后,对玻璃体析晶的影响不是简单的加合,复合的作用更为突出,进一步降低了玻璃的转变温度和析晶温度,整体均匀析出云母晶体.

Phase-separation and crystallization of SiO2 - Al2O3 - MgO - K2O - ( F, Cr2O3 ) glass

The influences of fluorine and chorine oxide and their mixture effects as nucleating agents on the nucleation and crystallization in the SiO_2-Al_2O_3-MgO-K_2O glass were investigated by using XRD, SEM and DTA techniques. The results showed that only fluorine were introduced to the base glass, mica crystals precipitated at the surface, as the results of prior phase-separation. While only chorine oxides were incorporated to base glass, the volume crystallization occurred but no mica crystals were formed because of the absence of fluorine. In each case the glass transition temperature was lower than that of the glass without fluorine and Cr_2O_3. However, when both fluorine and chorine oxides were incorporated to glass network, the effects on the nucleation and crystallization were strengthened and glass transition temperature (T_g) decreased greatly. Magnesium (aluminum) chromium spinel, Mg(Al_(1.5)Cr_(0.5))O_4, was formed at the much lower temperature, which was attributed to the weakness of glass network for the introduction of fluorine. Furthermore it was precipitation of the spinel that induced the richer of fluorine, resulting in the crystallization of bulk-activated mica crystalline phase.